3.1
Naltrexone (Nalorex, Bristol-Myers Squibb Pharmaceuticals Ltd) is an opioid antagonist with a high affinity for opioid receptors. It competitively displaces opioid agonists (for example, diamorphine or methadone), blocking the euphoric and other effects of opioids and thereby minimising the positive rewards associated with their use. The summary of product characteristics (SPC) states that naltrexone is licensed for use as an adjunctive prophylactic treatment for detoxified formerly opioid-dependent people (who have remained opioid free for at least 7 to 10 days). There are unlicensed long-lasting formulations of naltrexone in development (depot preparations and implants), but these do not fall within the scope of this appraisal.